Three-dimensional (3-D) imaging and display using two-dimensional (2-D) display devices has been attempted using various techniques. Stereoscopic techniques can display large images with high resolution. However, stereoscopic techniques typically require that the viewer wear special glasses to have a 3-D visual effect. Furthermore, stereoscopic techniques provide viewers with only horizontal parallax and a limited number of viewpoints. Additionally, viewers using stereoscopic glasses may suffer visual fatigue due to convergence-accommodation conflict.
Holography has also been used for 3-D displays. Using this technique, true 3-D images with full parallax and continuous viewing points may be produced using diffraction gratings. However, to obtain a proper grating, coherent light is needed when the hologram is recorded. Alternatively, computer-generated holograms can be made, but this approach requires lengthy computation time. Therefore, it is difficult to obtain large, color, 3-D displays using holography.
Integral imaging, or real-time integral photography, displays 3-D images in space by crossing incoherent light rays from 2-D elemental images, using a lenslet array. Like holography, integral imaging produces true 3-D images with full parallax and continuous viewing points. However, because lenslet arrays are used, the viewing angle, depth of focus, and resolution of the 3-D images is limited. Additionally, 3-D images produced in direct pick-up integral imaging are pseudoscopic (reversed-depth) images.
FIG. 1 depicts one embodiment of a prior art integral imaging and display system 100. The system 100 includes an imaging system 145 and a display system 175. The imaging system 145 includes a lens array 110 and an imaging sensor 120. The lens array 110 focuses images of an object 140 onto the image sensor 120, producing elemental images. The display system 175 includes a display panel 150 and a lens array 160. The display panel 150 generates 2-D elemental images 170 that are focused by the lens array 160 into a reconstructed 3-D image 170.
FIG. 2 depicts an embodiment of a prior art display system 175 to increase the depth range of the 3D image 170. As shown in FIG. 2, to increase the depth range requires macromovement of the lens array 160.
FIG. 3 depicts an embodiment of a prior art display system 200, that uses a concave mirror array 190 instead of a lens array.
A similar approach to that found in FIG. 3 uses a micro-convex mirror array. This technique is described in “Three-dimensional projection integral imaging using micro-convex mirror arrays” by Ju-Seog Jang and Bahram Javidi. Use of micro-convex mirror arrays may increase the viewing angle, because the micro-convex mirrors can be produced with a small f number (the ratio of the focal length of the lens to its effective aperture) with negligible aberration. Furthermore, when elemental images obtained from direct camera pickup with a 2-D image sensor and a lenslet array, 3-D orthoscopic virtual images are displayed. Flipping-free viewing of 3-D images is thus possible, even if optical barriers are not used, because each elemental image is projected only onto its corresponding micro-convex mirror. However, this technique using a micro-convex mirror array allows for only limited depth of focus for displayed 3-D images. The limitation to the depth of focus in turn limits the depth range of the displayed image.
Therefore, what is needed is an integral imaging and display system that provides improved depth range for 3-D images.